Create ClassLocking

3 files changed, 61 insertions, 0 deletions

diff --git a/vespajlib/src/main/java/com/yahoo/concurrent/classlock/ClassLock.java b/vespajlib/src/main/java/com/yahoo/concurrent/classlock/ClassLock.java
new file mode 100644
index 00000000000..2a3c70d31d2
--- /dev/null
+++ b/vespajlib/src/main/java/com/yahoo/concurrent/classlock/ClassLock.java
@@ -0,0 +1,19 @@
+package com.yahoo.concurrent.classlock;
+
+/**
+ * @author valerijf
+ */
+public class ClassLock implements AutoCloseable {
+    private final Class<?> clazz;
+    private final ClassLocking classLocking;
+
+    ClassLock(ClassLocking classLocking, Class<?> clazz) {
+        this.classLocking = classLocking;
+        this.clazz = clazz;
+    }
+
+    @Override
+    public void close() {
+        classLocking.unlock(clazz, this);
+    }
+}
diff --git a/vespajlib/src/main/java/com/yahoo/concurrent/classlock/ClassLocking.java b/vespajlib/src/main/java/com/yahoo/concurrent/classlock/ClassLocking.java
new file mode 100644
index 00000000000..8014148cc30
--- /dev/null
+++ b/vespajlib/src/main/java/com/yahoo/concurrent/classlock/ClassLocking.java
@@ -0,0 +1,37 @@
+package com.yahoo.concurrent.classlock;
+
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * @author valerijf
+ */
+public class ClassLocking {
+    private final Map<Class<?>, ClassLock> classLocks = new HashMap<>();
+    private final Object monitor = new Object();
+
+    public ClassLock lock(Class<?> clazz) {
+        synchronized (monitor) {
+            while(classLocks.containsKey(clazz)) {
+                try {
+                    monitor.wait();
+                } catch (InterruptedException ignored) { }
+            }
+
+            ClassLock classLock = new ClassLock(this, clazz);
+            classLocks.put(clazz, classLock);
+            return classLock;
+        }
+    }
+
+    void unlock(Class<?> clazz, ClassLock classLock) {
+        synchronized (monitor) {
+            if (classLock.equals(classLocks.get(clazz))) {
+                classLocks.remove(clazz);
+                monitor.notifyAll();
+            } else {
+                throw new IllegalArgumentException("Lock has already been released");
+            }
+        }
+    }
+}
diff --git a/vespajlib/src/main/java/com/yahoo/concurrent/classlock/package-info.java b/vespajlib/src/main/java/com/yahoo/concurrent/classlock/package-info.java
new file mode 100644
index 00000000000..010af471f03
--- /dev/null
+++ b/vespajlib/src/main/java/com/yahoo/concurrent/classlock/package-info.java
@@ -0,0 +1,5 @@
+// Copyright 2017 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+@ExportPackage
+package com.yahoo.concurrent.classlock;
+
+import com.yahoo.osgi.annotation.ExportPackage;